It depends on what type of publication you are selecting. For Example, if you select conference paper, ResearchGate does not include DOI automatically. Facing same issue here:
(PDF) Enhancement of Tube Side Heat Transfer using Twisted Stainless-Steel Angle (researchgate.net)
The automatic assignment of a DOI (Digital Object Identifier) to your article can depend on various factors and policies set by the publisher, journal, or platform where you are submitting your article. Here are some potential reasons why you might not see automatic DOI assignment:
Journal Policies: Different journals and publishers have their own policies regarding DOI assignment. Some journals provide DOIs automatically upon acceptance, while others may require authors to request DOIs separately or offer them as part of specific publication packages.
Submission Process: Make sure you have followed the correct submission process for the journal or platform you are using. Some platforms ask authors to input or request DOIs during the submission process, and failure to do so may result in a DOI not being automatically assigned.
Payment or Membership: In some cases, automatic DOI assignment may be contingent on payment or membership in a particular organization or society. Ensure that you have met any financial or membership requirements if applicable.
Technical Issues: There may be technical issues with the journal's submission system or the DOI assignment system. Contact the journal's technical support or editorial office for assistance if you suspect technical problems.
Article Status: DOIs are typically assigned at specific stages of the publication process, such as acceptance or publication. If your article is still in the review or revision phase, a DOI may not be assigned until it reaches the appropriate stage.
Journal-Specific DOI Policies: Some journals may have specific DOI policies, including whether they provide DOIs for certain types of content (e.g., articles, conference proceedings, data sets) or whether they use a different system for identification.
Author Responsibility: In some cases, authors may be responsible for obtaining DOIs independently through a DOI registration agency. Ensure you understand the requirements for DOI assignment at the journal or platform you are submitting to.
Changes in Journal Policies: Journal policies can change over time. If automatic DOI assignment was previously available but is no longer the case, it could be due to a change in the journal's policies or practices.
To address this issue, I recommend the following steps:
Review the submission guidelines and policies of the journal or platform where you are submitting your article. Look for any specific instructions regarding DOI assignment.
Contact the journal's editorial office or technical support for clarification on their DOI assignment process and to inquire about the status of your DOI.
Ensure that you have completed all required steps during the submission process, including any requests for DOI assignment.
If you believe there is a technical issue preventing DOI assignment, report the issue to the journal's technical support for resolution.
By following these steps and communicating with the journal or platform's support team, you should be able to determine the reason for the lack of automatic DOI assignment for your article and take appropriate action to address it.